Influence of the Intracranial Contents on the Head Motion under Bone Conduction.

INTRODUCTION: The mechanism of non-osseous bone conduction pathways, involving the intracranial contents (ICC) of the skull, is still not well understood. This study aimed to investigate the influence of the ICC on the skull bone wave propagation, including dependence on stimulation location and coupling. METHODS: Three Thiel-embalmed whole-head cadaver specimens were studied before and after the removal of the ICC. Stimulation was via the electromagnetic actuators from commercial bone conduction hearing aids. Osseous pathways were sequentially activated by mastoid, forehead, and bone-anchored hearing aid location stimulation via a 5-Newton steel headband or percutaneously implanted screw. Non-osseous pathways were activated by stimulation on the eye and dura via a 5-Newton steel headband and a custom-made pneumatic holder, respectively. Under each test condition, the 3D motion of the superior skull bone was monitored at ∼200 points. RESULTS: The averaged response of the skull surface showed limited differences due to the removal of the ICC. In some isolated cases, the modal pattern on the skull surface showed a trend for an upshift (∼1/2 octave) in the observed natural frequencies for drained heads. This was also consistent with an observed trend for an upshift in the transition frequency in the estimated deformation across the lateral surfaces of the temporal bones. Such changes were consistent with the expected reduction in mass and damping due to the absence of the ICC. CONCLUSION: Overall, the ICC affect to a limited extent the motion of the skull bone, with a limited trend for a reduction of its natural frequencies.

Glacier Surface Motion Estimation from SAR Intensity Images Based on Subpixel Gradient Correlation.

With the current extensive availability of synthetic-aperture radar (SAR) datasets with high temporal (e.g., a repeat cycle of a few or a dozen days) and spatial resolution (e.g., in the order of ∼1 m), radar remote sensing possesses an increasing potential for the monitoring of glacier surface motion thanks to the nearly weather and time-independent advantages. This paper proposes a robust subpixel frequency-based image correlation method for dense matching and integrates the improved matching into a workflow of glacier surface motion estimation using SAR intensity images with specific pre-processing and post-processing steps. The proposed matching method combines complex edge maps and local upsampling in the frequency domain for subpixel intensity tracking, which ensure the accuracy and robustness of glacier surface motion estimation. Experiments were carried out with TerraSAR-X and Sentinel-1 images covering two glacier areas in pole and alpine regions. The results of the monitoring and investigation of glacier motion validate the feasibility and reliability of the presented motion estimation method based on subpixel gradient correlation. The comparative results using both simulated and real SAR data indicate that the proposed matching method outperforms commonly used correlation-based matching methods in terms of matching accuracy and the ability to obtain correct matches.

Technical Note: Investigating internal-external motion correlation using fast helical CT.

PURPOSE: To quantify the use of anterior torso skin surface position measurement as a breathing surrogate. METHODS: Fourteen patients were scanned 25 times in alternating directions using a free-breathing low-mA fast helical CT protocol. Simultaneously, an abdominal pneumatic bellows was used as a real-time breathing surrogate. The imaged diaphragm dome position was used as a gold standard surrogate, characterized by localizing the most superior points of the diaphragm dome in each lung. These positions were correlated against the bellows signal acquired at the corresponding scan times. The bellows system has been shown to have a slow linear drift, and the bellows-to-CT synchronization process had a small uncertainty, so the drift and time offset were determined by maximizing the correlation coefficient between the craniocaudal diaphragm position and the drift-corrected bellows signal. The corresponding fit was used to model the real-time diaphragm position. To estimate the effectiveness of skin surface positions as surrogates, the anterior torso surface position was measured from the CT scans and correlated against the diaphragm position model. The residual error was defined as the root-mean-square correlation residual with the breathing amplitude normalized to the 5th to 95th breathing amplitude percentiles. The fit residual errors were analyzed over the surface for the fourteen studied patients and reported as percentages of the 5th to 95th percentile ranges. RESULTS: A strong correlation was measured between the diaphragm motion and the abdominal bellows signal with an average residual error of 9.21% and standard deviation of 3.77%. In contrast, the correlations between the diaphragm position model and patient surface positions varied throughout the torso and from patient to patient. However, a consistently high correlation was found near the abdomen for each patient, and the average minimum residual error relating the skin surface to the diaphragm was 11.8% with a standard deviation of 4.61%. CONCLUSIONS: The thoracic patient surface was found to be an accurate surrogate, but the accuracy varied across the surface sufficiently that care would need to be taken to use the surface as an accurate and reliable surrogate. Future studies will use surface imaging to determine surface patch algorithms that utilize the entire chest as well as thoracic and abdominal breathing relationships.

Evaluation of thoracic surface motion during the free breathing and deep inspiration breath hold methods.

The aim of this study was to evaluate thoracic surface motion from chest wall expansion during free breathing (FB) and deep inspiration breath hold (DIBH) methods, measured with and without 4-dimensional computed tomography (4D-CT) simulation, using equipment developed in-house. The respiratory amplitude and chest wall expansion were evaluated at 5 levels of the thorax, (the sterno-clavicular joint (SCJ), the second level, the intermammary line (IML), the fourth level and the caudal end of the xiphoid process (XP)) using radiopaque wires and potentiometers, with a CT scan simultaneously. This study included 25 examinees (10 volunteers performed FB, 10 volunteers performed DIBH and 5 patients performed FB). For low and irregular respiration, coaching was used, and its impact was evaluated for both breathing methods, FB and DIBH. The breathing amplitude performed with FB between volunteers and patients was not detectable at the SCJ; increasing to the abdomen, 3 mm vs 2 mm (p = 0.326) at the second level; 6 mm vs 4 mm (p = 0.042) at the IML; 10 mm vs 8 mm (p < 0.01) at the fourth level; and 23 mm vs 19 mm (p < 0.001) at the XP. Contrary to the DIBH, where breathing amplitude was greater at 2 first levels 18 mm (SCJ) and 20 mm (second level), decreasing to the abdomen, 14 mm (IML); 11 mm (fourth level); and 10 mm (XP). Chest wall expansion was not detected at the SCJ, while at other levels measured from 1 to 7 mm. Coaching was improve breathing amplitude, for both methods, FB (3 mm) and DIBH (5 mm). The location of amplification is different depending on the breathing method and the in-house phantom was useful to check the amplification level.

Feedback contribution to surface motion perception in the human early visual cortex.

Human visual surface perception has neural correlates in early visual cortex, but the role of feedback during surface segmentation in human early visual cortex remains unknown. Feedback projections preferentially enter superficial and deep anatomical layers, which provides a hypothesis for the cortical depth distribution of fMRI activity related to feedback. Using ultra-high field fMRI, we report a depth distribution of activation in line with feedback during the (illusory) perception of surface motion. Our results fit with a signal re-entering in superficial depths of V1, followed by a feedforward sweep of the re-entered information through V2 and V3. The magnitude and sign of the BOLD response strongly depended on the presence of texture in the background, and was additionally modulated by the presence of illusory motion perception compatible with feedback. In summary, the present study demonstrates the potential of depth-resolved fMRI in tackling biomechanical questions on perception.

Preoperative Evaluation of Tumor Adhesion to Adjacent Brain Tissue in Patients with Meningioma with BSMI Method and Its Comparison with the Width of Edema Around Tumor

Background: This study aims to investigate the ability of BSMI, to preoperative evaluation of tumor adhesion to adjacent brain tissue in patients with meningioma and comparing this method to the width of edema around tumor, using surgery findings as the reference standard. Methods: Thirty patients with meningioma brain tumor who underwent surgery at Loghman hospital were selected for the study between November 2016 and January 2018. The level of edema according to the classification of Ide et al., (u1995) was compared with the surgical findings with blinded results, and neurosurgeons made a qualitative assessment of tumor adhesion at the time of resection. The ability of BSMI and level of edema to predict the surgical assessment of adhesion was tested using the Fisher Exact Test. Results: BSMI method was conducted on patients with meningioma brain tumor, which judged 22 (73.3%) patients as adhesion (+) and 8 (26.66%) patients as adhesion (-). In this case, there was a significant relationship between BSMI judgment and surgical findings (p-value<0.0001). The sensitivity, specificity, precision and accuracy was high, at 91.30%, 85.71%, 95.45% and 90%, respectively. Using T2-Weighted SPACE sequence, of the 30 patients, 13 (43.3%) were judged as adhesion (+) and 17 (56.7%) as adhesion (-) from edema, whereas surgical findings evaluated 23 (76.7%) as adhesion (+) and 7 (23.3%) as adhesion (-).The sensitivity was moderate but the specificity was high, at 52.17% and 85.71%, respectively. Other criteria such as precision and accuracy were 62.31% and 60%, respectively. Conclusions: BSMI evaluated adhesion of the tumor to the adjacent brain tissue with high-accuracy prior to surgery. This method was more effective than Edema method in evaluating adhesion between meningioma and the brain.

Which motion segments are required to sufficiently characterize the kinematic behavior of the trunk?

Various kinematic definitions of the thoracic spine have been employed in past work. However, the segments necessary to sufficiently characterize the thoracic spine during trunk movements in all three planes of motion have not yet been identified. This study aimed to determine the minimum number of segments necessary to adequately characterize the kinematics of the thoracic spine. Thirty individuals, asymptomatic for back pain, performed ten trials of maximum trunk flexion, lateral bend, and axial twist; thoracic flexion, lateral bend, and axial twist; and slumped standing. Marker clusters were applied over the C(7), T(3), T(6), T(9), T(12), and L(5) vertebrae. Three-dimensional angles of each cluster were calculated, and cross-correlation (R(xy(time))) and correlation (R(xy(max))) analyses were employed to assess the relationships in the motion patterns and maximum angles of adjacent clusters, respectively. The motion patterns and maximum angles of adjacent clusters were very strongly (R(xy(time)) > 0.90 for 26 of 35 pairings) and strongly (R(xy(max)) > 0.80 for 25 of 35 pairings) correlated, respectively. A four-cluster set (C(7), T(6), T(12), and L(5)) represented thoracic movement for six of the seven movement tasks tested. These results provide insight into thoracic movement coordination, with implications for predictive spinal modeling and clinical assessment practices.